Volatile fields with inconsistent synchronization in IpcClient #1991

Affected version: HEAD

File: maven-resolver-named-locks-ipc/src/main/java/org/eclipse/aether/named/ipc/IpcClient.java:78-87

Fields initialized, socket, output, input, receiver are volatile but their compound use (read + method call) lacks synchronization. send() reads output into a local variable at line 316 without holding the monitor, then synchronizes on the local reference at line 323, but close() nulls output under synchronized(this) at line 361. receive() has the same pattern with input.

Originally reported in #1944.